1. Field of the Invention
The present invention relates generally to an improved system for inspecting textured surfaces and detecting defects, and particulate contaminants on a surface and in particular to an improved method and system for inspecting textured surfaces, with improved resolution. Still more particularly, the present invention provides an improved system for inspecting textured surfaces and detecting defects, and contaminants on such a surface through the use of a shaped spatial filter and a reference optical beam.
2. Description of the Related Art
Disks used for recording data may contain various surface structures such as defects, particulate contaminants, and surface texture. Presently, the high-recording densities on thin-film disks and the head/disk tribology require that the disks be free of defects and particulate contaminants. Most defects and contaminants, which were previously acceptable on particulate-oxide media disks, are unacceptable on thin-film disks. To detect such fine defects and contaminants, high-resolution instruments are required.
In addition, texturing of disks is required to control stiction properties of the disk. Texture is intentionally added to a disk to provide low friction or "stiction" when a magnetic head is sliding or resting on the disk. Presently, disk drive motors are very small, resulting in an inability to spin the disks up to a proper speed if too much friction or stiction is present. Therefore, it is critical to maintain a proper level of friction or stiction. Older disks drives possessed enough power such that friction or stiction was not as much of a concern.
Prior to the present invention, the level of texture or roughness was monitored with a mechanical stylus instrument that contacted the surface of the disk. This type of instrument, involving a contact method, is slow and time consuming. As a result, it is not economically possible to test every disk manufactured. As a result, disks were sampled and assumptions were made that the remainder of the disks in the sample group were of the same texture. This assumption, however, is not accurate since small changes in a manufacturing process may change the texture. Some systems have been developed to measure texture by collecting and measuring light scattered from a disk due to the texturing. Integrating spheres have been utilized, however, such spheres collect light from all structures on the disk which scatter light. This results in errors since the scattered light includes scattering, as a result of the textured surface, previous polishing, carbon impurities, and other microstructures or particles.
Therefore, it would be desirable to have a method and system capable of collecting and measuring light scattered off a disk surface as a result of the texture of the surface or defects and particles on the surface.